I just received some paristaltic pumps in the mail today thanks to Ryan Donovan. I have been playing around with them for a few hours and they seem to work pretty well for their cost.
Here is a link to them.
http://www.ebay.com/itm/Dosing-pump...247?pt=LH_DefaultDomain_0&hash=item5d3ba567a7
They definitely aren't as high quality as a dosing pump you'd pay $60-$100 for and are a little finicky, but for $15 what do you expect? Running at 12v they seem to have a pretty consistent dosing rate of 0.625ml/second. I haven't measured the flow at lower voltages yet.